Power semiconductor devices are used for switching circuits and inverter circuits for power control.
A power semiconductor device needs to have a high breakdown voltage and a low on-resistance, but limits of the breakdown voltage and on-resistance of a power semiconductor device using silicon (Si) based on physical properties of Si are being reached.
On the other hand, a nitride semiconductor has a wider band gap than Si so that a semiconductor device using a nitride semiconductor can implement properties combining a lower on resistance and a higher breakdown voltage more easily than a semiconductor device using silicon.
Field effect transistors (FET) using a nitride semiconductor are grouped into a normally-on type and a normally-off type. Normally-off type FETs have an advantage of a small number of components when a power control circuit is constructed, but have problems such as a slower switching speed, an increased on-resistance, and further difficulty of implementing a desired threshold voltage within a normally-off range.